We know that communication is key when it comes to a successful relationship. But there are just certain topics you must be able to discuss before you can know you've found the One.

"True intimacy requires openness and transparency," explains psychotherapist and relationship expert Toni Coleman. "In an intimate relationship, the individuals need to feel they can be themselves, warts and all, and know that they will be loved and accepted for who they truly are, with all the imperfections and history they bring to the relationship."

So, with that in mind, here are six things you must be able to discuss before you take the next big step.

1. Your expectations

Whether you can admit it or not, "everyone has expectations about relationships and their partner’s role," says Lesli Doares, marriage coach and author of Blueprint for a Lasting Marriage. "You will end up holding each other accountable to those expectations," she says. So before you make a major commitment, you must be able to bring those expectations to the table. "Once they are out there, you can have a conversation about whether those expectations make sense and if you both agree to them," Doares says. "This way, you have a clear understanding of what the relationship will look like and each of your responsibilities to make it happen."

2. Your emotional vulnerabilities

You may not want to be vulnerable with anyone, but "when two people can expose their deepest vulnerabilities to each other, it creates a deep and intimate bond between them," says Coleman, and that's the kind of bond you need for a lasting relationship. "They know that whatever happens, their partner will be on their side, understand what they need, and have their back," she says. "This is powerful relationship glue that can keep a marriage together through the worst that life can dish out."

3. Physical intimacy and sex

Physical affection is a very important component to a healthy relationship. But sex isn't always easy to talk about, Doares says, because it's so personal. "[Sex] is highly susceptible to external factors such as stress, age, physical health, and overall satisfaction with the relationship," she says. "Changes here are often a warning about the health of the relationship. Being able to be open about your likes and dislikes, frequency and kind of intimacy, fantasies, disappointments, and more can keep this part of your relationship from getting stale."

4. Your past relationships

You likely dated a few duds before you found your perfect match. And while you might prefer to keep them in the past, Coleman says being able to discuss them openly is important. "If people can’t discuss their past relationships with their partner, it’s likely there are unresolved feelings and issues that could spell trouble in their present relationship," she warns. "Everyone has a past, and most people have exes that they are no longer with because those relationships were not the right ones for them. Ideally, they would have reached some closure and acceptance before starting a new relationship."

5. Your finances

Like sex, money can be tough to talk about. "Some couples like to keep it all separate because finding common ground can be so difficult," says Doares. "But not talking about it doesn’t change its impact on the relationship. Each of your relationships with money is a reflection of how you grew up, what it means to you, and how it supports or undermines the kind of life you want. Not talking about it can put a barrier between you because the chance that you will both have exactly the same income and expenses throughout your life together is highly unlikely. One person will eventually feel like less of a partner, and that will not bode well for the success of the relationship."

6. Any concerns you have about the relationship

No relationship is completely perfect, even when you've found the One. So, "if a partner can’t openly discuss concerns regarding something in the relationship, whatever that something is will fester and grow over time," says Coleman. "It is the small issues that build into larger ones over time and, if not dealt with, lead to emotional distance, resentment, conflict, and even greater misunderstandings."